DrVarnik on YouTube has posted a tutorial video on how to receive, decode and plot AIS information. The Automatic Identification System (AIS) is a system used for automatic tracking of large ships and passenger boats. It is a similar idea to tracking aircraft with ADS-B. His method uses a RTL-SDR for receiving the AIS signals with SDRSharp, decoding received signals with AISMon and plotting the decoded information with OpenCPN. He uses VB-Cable for looping the audio from SDRSharp to AISMon, but if you have a ‘Stereo Mix’ or equivalent feature with your soundcard, that will be unneeded. Best results will be achieved using a narrow-band vertically polarized antenna tuned for 161.975 MHz and 162.025 MHz (marine VHF). A directional antenna would also likely be a benefit. You can find some designs to try lower down the page. For safety, please only use this guide on land! Wouldn’t want you getting lost at sea.